Big time doubts, too high rate and no explanation what will they do with the money.
actually there is an explanation on the site if you checked it out. and someone even explained it above your comment
now lets talk about whether it is a Ponzi scheme or if it is going to be the run away plan.
I don't say it is fully ponzi scheme, but in any case site owner faces significant losses from these bitcoin mining businesses then anything can happen. So your coins or investments are at high risk on these kinds of sites. Until now they are paying on time for all their faucet users, but at the same time, they never explained how they are picking up the lottery winners even those many times people request on this forum. It shows that they are not entirely honest in doing business, so your investments are always at high risk.